ProjectSummary Duchennemusculardystrophy(DMD)isalethal,progressive,muscle-wastingdiseasethatinvolvesdefectsin theregenerativecapacityofthepathologicalmuscle.Inrecentyears,expandingknowledgeofepigenetic mechanismsthatinfluencemusclegrowthandregenerationhasshownthatmanipulatingthosemechanisms canbetherapeuticallyuseful.Thefocusofourstudyistodeterminefactorsthataffecttheexpressionof importantepigeneticregulatorsthatcaninfluencegeneexpressioninskeletalmusclestemcells,called satellitecells.WewilltestthenovelhypothesisthattheproteinKlotho(KL)influencesmyogenesisthroughthe epigeneticregulationofsatellitecellactivationanddifferentiation,therebyaffectingmuscleregeneration.We willinvestigatethisthroughthefollowingaims: Aim1.DeterminewhetherKLinfluencessatellitecellactivationanddifferentiationthroughchangesinhistone methylation.Wewillassaywhetherdown-regulationofspecifichistonedemethylasesinmuscleisasignificant componentofthemechanismthroughwhichKLaffectssatellitecellproliferationandexpressionofmyogenic regulatorygenes.WewillalsoassayforgenesthatexperiencechangesinhistonemethylationatH3K27in musclecellsstimulatedwithKL. Aim2.DeterminewhethermanipulatingKLexpressionaffectshistonemethylationinsatellitecellsfrommdx mice,amodelforDMD.Wewillassayforchangesinnucleartargetingorexpressionofspecifichistone demethylasesthatresultfromgeneticallyrestoringKLexpressiontodystrophic,mdxmice.Wewillalsoassay forgenesexperiencingchangesinH3K27methylation,causedbyKLtransgeneexpressioninmdxmice WeanticipatethatourfindingswillestablishnovelregulatoryrolesforKL,inwhichtheproteinplaysan epigeneticregulatoryrolethataffectsmyogenesis.Furthermore,theresultsfromthisstudycanprovidethe identityofnewtherapeutictargetstotreatDMDbyimprovingmuscleregeneration.